Technical Abstract:
Land managers in northwestern Colorado have identified that riparian areas are more important than uplands for the ecology, management, and economics of local ranches. We compare stream morphology and vegetation of nine 30 meter reaches with and without cottonwoods (open vs. closed canopy) on two adjacent streams (Elkhead and Calf Creeks ) to determine whether wooded vs. non-wooded reaches can be considered alternate states. Reach morphology was characterized using Rosgen stream classification based on slope, sinuosity, entrenchment, width, depth and channel bed composition. Vegetation cover by species was measured in each hydrologically unique component (near-stream vs. far). Analysis of Variance (ANOVA) was used to determine vegetation and stream morphology variables that were significantly different between open and closed reaches. Closed canopy reaches had a wider, finer sediment channel, a broader floodplain and lower forb and sedge/rush cover (near stream) that open reaches. This pilot study suggest that while some variation is found in vegetation and stream morphology according to canopy cover, the largest differences in both morphology and vegetation are between the two streams themselves, even though they are adjacent and have similar management. This finding represents the challenge for generalizing the effects of management across multiple streams. Sampling on a large scale might reduce variation between streams and aid in the development of alternate riparian states.